1. Field of the Invention
The present invention relates to a zero or low insertion force electrical connector for connecting one printed circuit board to another. More particularly, this invention relates to a zero insertion force connector that yields greater densities and that allows greater deflection of the connector contacts.
2. Prior Art
There are many types of electrical connectors in the prior art for making electrical connections to conductive strips dispersed along opposing sides on the elongated edge of a printed circuit board. One such type is called a "zero insertion force" connector, which allows a circuit board to be inserted into the connector without any substantial insertion force. The board is thus inserted into the connector to make an electrical connection without any urging and potentially harmful friction force against the delicate electrical contacts on the opposing sides of the edge of the board.
Examples of these types of connectors are shown in U.S. Pat. Nos. 3,701,071, 3,795,088, 3,920,303, 3,848,952, 4,176,917, and 4,575,172. While these prior art connectors have provided low insertion force connectors for printed circuit boards, they have deficiencies.
One problem is the limited beam deflection these connectors allow. These prior art connectors have typically employed C- or U-shaped contacts supported by a central attachment point. Depending on the location of the attachment joint, one or the other or both of the two contact arms have a shortened beam length. This shortened beam length limits the range that the contact can deflect without plastic deformation of the contact. Since many boards are or become warped through use, the limited deflection allowed by such a connector limits the utility of the connector for some significantly warped boards.
Another problem with the prior art connectors is the limited density of the electrical connections the connectors can accommodate between the boards they connect. C- or U-shaped contacts necessarily grip the board on two sides. This means one contact, i.e., one electrical connection, occupies a certain amount of contact pad space on both sides of the board. Since adjacent contact pads must be separated by a certain minimum distance given technological constraints, C-or U-shaped connectors cannot achieve a greater density than minimum distance allowed between contacts on one side of the board.